Four members of a family were killed in a wrong-way freeway crash in California that also took the lives of two other people, including the sister of a woman arrested on suspicion of drunken driving and manslaughter.

Two people in a Ford Explorer - Gregorio Mejia-Martinez, 47, and Ester Delgado - died at the scene of Sunday's early morning crash on State Route 60, said Los Angeles County coroner's Lt. Fred Corral.

Two other family members in the SUV - Leticia Ibarra, 42, and Jessica Jasmine Mejia, 20 - were declared dead at a hospital. All four were from Huntington Park.

Two additional victims were passengers in a Chevy Camaro that authorities said was driven by 21-year-old suspect Olivia Culbreath of Fontana. Her sister, Maya Louise Culbreath, 24, of Rialto and Kristin Melissa Young, 24, of Chino were declared dead at the scene, Corral said.

Olivia Culbreath remained hospitalized in serious condition and was being treated for a broken femur and a ruptured bladder. Meanwhile, investigators were seeking witnesses after the speeding Camaro careened the wrong way down the freeway, causing the violent crash.

Jimenez said the crash scene in Diamond Bar, a suburb east of Los Angeles, was horrific. Three people were ejected from their cars and the Camaro was barely recognizable.

Authorities said Culbreath was traveling north in the southbound lanes of State Route 57 before transitioning east in the westbound lanes where the Camaro collided head-on with the Ford Explorer. A Ford Freestyle then collided with the Explorer.

Evidence gathered at the scene included an alcoholic beverage, Jimenez told the San Gabriel Valley Tribune.

Witnesses told dispatchers the Camaro was speeding up to 100 mph, he said.